Procedural Worlds / Custom World
It feels like this suggestion has been made numerous times on the various platforms, but I could not find a current one on here.
What I'd like to suggest is a new Custom World option, where you could include settings for adding custom planets/moons from the workshop along with size, distance and variation settings.
The game would generate a world with potentially more planets than just the Star System start. This would make for much more varied worlds without the hassle of having to "handcraft" your own, encouraging exploration.